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package fish.payara.nucleus.requesttracing.store.strategy;

import fish.payara.notification.requesttracing.RequestTrace;
import java.util.Collection;
import java.util.Iterator;

/**
 * Strategy for finding traces that need removing from a list. Will remove the trace at the shortest traces in the given
 * set of traces. If multiple traces are equally short the oldest is removed first.
 */
public class LongestTraceStorageStrategy implements TraceStorageStrategy {

    /**
     * Gets the trace that needs removing. Removes the provided trace if present, or selects the shortest of the given
     * traces should their number be larger then maxSize.
     *
     * @see TraceStorageStrategy#getTraceForRemoval(Collection, int, RequestTrace)
     */
    @Override
    public RequestTrace getTraceForRemoval(Collection<RequestTrace> traces, int maxSize, RequestTrace traceToRemove) {
        if (traces == null || traces.isEmpty() || traces.size() <= maxSize) {
            return null;
        }
        return traceToRemove != null && traces.contains(traceToRemove) ? traceToRemove : findShortestTrace(traces);
    }

    private static RequestTrace findShortestTrace(Collection<RequestTrace> traces) {
        Iterator<RequestTrace> iter = traces.iterator();
        RequestTrace shortest = iter.next();
        while (iter.hasNext()) {
            RequestTrace next = iter.next();
            if (next.getElapsedTime() < shortest.getElapsedTime() 
                || next.getElapsedTime() == shortest.getElapsedTime() 
                    && next.getStartTime().isBefore(shortest.getStartTime())) {
                shortest = next;
            }
        }
        return shortest;
    }
}
